The following description provides a summary of information relevant to the present invention and is not a concession that any of the information provided or publications referenced herein is prior art to the presently claimed invention.
Saccharides, more commonly known as sugars, are organic compounds that play important roles in living organisms. Of particular medical and clinical interest is the monosaccharide D-glucose, which is a critical biochemical energy source for cells. Glucose is stored in the liver as glycogen, and is released as needed for energy consumption. The production and the consumption of glucose are regulated such that the concentration of glucose is relatively constant in the body fluids of a normal or healthy mammals. A disruption of this regulation of glucose can be associated with diseases such as diabetes and adrenal insufficiency in humans.
The detection of glucose in the blood or the urine provides valuable information for the diagnosis of these diseases. Electrochemical detection of saccharides by enzymatic decomposition of saccharides is known. One particular assay utilizes the enzyme glucose oxydase, which decomposes glucose to release hydrogen peroxide. The hydrogen peroxide can be measured by an electrode. A problem with this assay is that the enzymatic activity of the naturally occurring enzyme degrades with time. Thus the sample cannot be recycled for repeated assays because the glucose and enzyme have degraded. Further, this susceptibility to degradation makes the assay vulnerable to imprecision.
Recent approaches to detect saccharides involve the use of synthetic molecular receptors that bind to saccharides and exhibit a non-enzymatic chemically detectable change upon binding with the saccharide. Specifically, receptor molecules that incorporate boronic acid moieties have been shown to bind to saccharides through covalent interactions in aqueous basic media. The most common interaction is with cis-1,2- or 1,3-diols of saccharides to form five- or six-membered rings respectively.
Recently, a simple boronic acid receptor was reported that binds and detects sorbitol, fructose, and glucose by electrochemical changes. xe2x80x9cRedox switching of carbohydrate binding to ferrocene boronic acidxe2x80x9d, A. N. J. Moore, D. D. M. Wayner, Canadian Journal of Chemistryxe2x80x94Revue Canadienne De Chimie, 77, 681 (1999). This monoboronic acid receptor exhibited selectivity for D-fructose. This is consistent with early reports that monoboronic acids have an inherent selectivity for D-fructose. xe2x80x9cPolyol complexes and structure of the benzeneboronate ionxe2x80x9d J. P. Lorand, J. D. Edward, Journal of Organic Chemistry 1959, 24, 769.
Although glucose may be detected electrochemically the above receptor, the receptor is not selective for glucose and the presence of other saccharides will interfere with any assay utilizing such a receptor. Unfortunately, the most common glucose measurement applications use complex samples such as plasma and the large number of interfering compounds make electrochemical determinations very difficult if not impossible. What is needed is a selective molecular receptor system for detecting glucose having the specificity required for clinical assays of complex samples.
The invention satisfies this need. The invention provides compounds for detecting sacchharides by electrochemistry. The compounds comprise a first boronic acid group attached by a first linker group to a first tertiary amine, the first tertiary amine attached to a reporter group comprising an organometalic reporter moiety, the first tertiary amine further attached by a spacer group to a second tertiary amine, the second tertiary amine attached to an R group and a second linker group, and the second linker group attached to a second boronic acid group. In preferred embodiments, the compound selectively detects glucose and has a higher stability constant for glucose than for other saccharides
The invention includes a method for detecting saccharides in a sample comprising the steps of providing a compound of the invention; treating the sample with the compound; and detecting saccharides bound to the compound. In a preferred embodiment, the compound has the formula herein below and the method for detecting saccharides selectively detects glucose. 